SUBROUTINE iau_DAT ( IY, IM, ID, FD, DELTAT, J ) *+ * - - - - - - - - * i a u _ D A T * - - - - - - - - * * For a given UTC date, calculate Delta(AT) = TAI-UTC. * * :------------------------------------------: * : : * : IMPORTANT : * : : * : A new version of this routine must be : * : produced whenever a new leap second is : * : announced. There are five items to : * : change on each such occasion: : * : : * : 1) The parameter NDAT must be : * : increased by 1. : * : : * : 2) The set of DATA statements that : * : initialize the arrays IDAT and : * : DATS must be extended by one line. : * : : * : 3) The parameter IYV must be set to : * : the current year. : * : : * : 4) The "Latest leap second" comment : * : below must be set to the new leap : * : second date. : * : : * : 5) The "This revision" comment, later, : * : must be set to the current date. : * : : * : Change (3) must also be carried out : * : whenever the routine is re-issued, : * : even if no leap seconds have been : * : added. : * : : * : Latest leap second: 2016 December 31 : * : : * :__________________________________________: * * This routine is part of the International Astronomical Union's * SOFA (Standards of Fundamental Astronomy) software collection. * * Status: user-replaceable support routine. * * Given: * IY i UTC: year (Notes 1 and 2) * IM i month (Note 2) * ID i day (Notes 2 and 3) * FD d fraction of day (Note 4) * * Returned: * DELTAT d TAI minus UTC, seconds * J i status (Note 5): * 1 = dubious year (Note 1) * 0 = OK * -1 = bad year * -2 = bad month * -3 = bad day (Note 3) * -4 = bad fraction (Note 4) * -5 = internal error (Note 5) * * Notes: * * 1) UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper * to call the routine with an earlier date. If this is attempted, * zero is returned together with a warning status. * * Because leap seconds cannot, in principle, be predicted in * advance, a reliable check for dates beyond the valid range is * impossible. To guard against gross errors, a year five or more * after the release year of the present routine (see parameter IYV) * is considered dubious. In this case a warning status is returned * but the result is computed in the normal way. * * For both too-early and too-late years, the warning status is J=+1. * This is distinct from the error status J=-1, which signifies a * year so early that JD could not be computed. * * 2) If the specified date is for a day which ends with a leap second, * the TAI-UTC value returned is for the period leading up to the * leap second. If the date is for a day which begins as a leap * second ends, the TAI-UTC returned is for the period following the * leap second. * * 3) The day number must be in the normal calendar range, for example * 1 through 30 for April. The "almanac" convention of allowing * such dates as January 0 and December 32 is not supported in this * routine, in order to avoid confusion near leap seconds. * * 4) The fraction of day is used only for dates before the introduction * of leap seconds, the first of which occurred at the end of 1971. * It is tested for validity (0 to 1 is the valid range) even if not * used; if invalid, zero is used and status J=-4 is returned. For * many applications, setting FD to zero is acceptable; the * resulting error is always less than 3 ms (and occurs only * pre-1972). * * 5) The status value returned in the case where there are multiple * errors refers to the first error detected. For example, if the * month and day are 13 and 32 respectively, J=-2 (bad month) will be * returned. The "internal error" status refers to a case that is * impossible but causes some compilers to issue a warning. * * 6) In cases where a valid result is not available, zero is returned. * * References: * * 1) For dates from 1961 January 1 onwards, the expressions from the * file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used. * * 2) The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of * the 1992 Explanatory Supplement. * * Called: * iau_CAL2JD Gregorian calendar to JD * * This revision: 2023 January 17 * * SOFA release 2023-10-11 * * Copyright (C) 2023 IAU SOFA Board. See notes at end. * *----------------------------------------------------------------------- IMPLICIT NONE INTEGER IY, IM, ID DOUBLE PRECISION FD, DELTAT INTEGER J * Release year for this version of iau_DAT INTEGER IYV PARAMETER ( IYV = 2023 ) * Number of Delta(AT) changes (increase by 1 for each new leap second) INTEGER NDAT PARAMETER ( NDAT = 42 ) * Number of Delta(AT) expressions before leap seconds were introduced INTEGER NERA1 PARAMETER ( NERA1 = 14 ) * Dates (year, month) on which new Delta(AT) came into force INTEGER IDAT(2,NDAT) * New Delta(AT) which came into force on the given dates DOUBLE PRECISION DATS(NDAT) * Reference dates (MJD) and drift rates (s/day), pre leap seconds DOUBLE PRECISION DRIFT(2,NERA1) * Miscellaneous local variables LOGICAL MORE INTEGER JS, M, N, IS DOUBLE PRECISION DA, DJM0, DJM * Dates, Delta(AT)s, reference dates, and drift rates DATA ((IDAT(M,N),M=1,2),DATS(N),(DRIFT(M,N),M=1,2),N=1,14) : / 1960, 1, 1.4178180D0, 37300D0, 0.001296D0, : 1961, 1, 1.4228180D0, 37300D0, 0.001296D0, : 1961, 8, 1.3728180D0, 37300D0, 0.001296D0, : 1962, 1, 1.8458580D0, 37665D0, 0.0011232D0, : 1963, 11, 1.9458580D0, 37665D0, 0.0011232D0, : 1964, 1, 3.2401300D0, 38761D0, 0.001296D0, : 1964, 4, 3.3401300D0, 38761D0, 0.001296D0, : 1964, 9, 3.4401300D0, 38761D0, 0.001296D0, : 1965, 1, 3.5401300D0, 38761D0, 0.001296D0, : 1965, 3, 3.6401300D0, 38761D0, 0.001296D0, : 1965, 7, 3.7401300D0, 38761D0, 0.001296D0, : 1965, 9, 3.8401300D0, 38761D0, 0.001296D0, : 1966, 1, 4.3131700D0, 39126D0, 0.002592D0, : 1968, 2, 4.2131700D0, 39126D0, 0.002592D0 / * Dates and Delta(AT)s DATA ((IDAT(M,N),M=1,2),DATS(N),N=15,30) : / 1972, 1, 10D0, : 1972, 7, 11D0, : 1973, 1, 12D0, : 1974, 1, 13D0, : 1975, 1, 14D0, : 1976, 1, 15D0, : 1977, 1, 16D0, : 1978, 1, 17D0, : 1979, 1, 18D0, : 1980, 1, 19D0, : 1981, 7, 20D0, : 1982, 7, 21D0, : 1983, 7, 22D0, : 1985, 7, 23D0, : 1988, 1, 24D0, : 1990, 1, 25D0 / DATA ((IDAT(M,N),M=1,2),DATS(N),N=31,NDAT) : / 1991, 1, 26D0, : 1992, 7, 27D0, : 1993, 7, 28D0, : 1994, 7, 29D0, : 1996, 1, 30D0, : 1997, 7, 31D0, : 1999, 1, 32D0, : 2006, 1, 33D0, : 2009, 1, 34D0, : 2012, 7, 35D0, : 2015, 7, 36D0, : 2017, 1, 37D0 / * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * Initialize the result to zero and the status to OK. DA = 0D0 JS = 0 * If invalid fraction of a day, set error status and give up. IF ( FD.LT.0D0 .OR. FD.GT.1D0 ) THEN JS = -4 GO TO 9000 END IF * Convert the date into an MJD. CALL iau_CAL2JD ( IY, IM, ID, DJM0, DJM, JS ) * If invalid year, month, or day, give up. IF ( JS .LT. 0 ) GO TO 9000 * If pre-UTC year, set warning status and give up. IF ( IY .LT. IDAT(1,1) ) THEN JS = 1 GO TO 9000 END IF * If suspiciously late year, set warning status but proceed. IF ( IY .GT. IYV+5 ) JS = 1 * Combine year and month. M = 12*IY+IM * Find the most recent table entry. IS = 0 MORE = .TRUE. DO 1 N=NDAT,1,-1 IF ( MORE ) THEN IS = N MORE = M .LT. ( 12*IDAT(1,N) + IDAT(2,N) ) END IF 1 CONTINUE * Prevent underflow warnings. IF ( IS .LT. 1 ) THEN JS = -5 GO TO 9000 END IF * Get the Delta(AT). DA = DATS(IS) * If pre-1972, adjust for drift. IF ( IS .LE. NERA1 ) DA = DA + : ( DJM + FD - DRIFT(1,IS) ) * DRIFT(2,IS) * Return the Delta(AT) value and the status. 9000 CONTINUE DELTAT = DA J = JS * Finished. *+---------------------------------------------------------------------- * * Copyright (C) 2023 * Standards of Fundamental Astronomy Board * of the International Astronomical Union. * * ===================== * SOFA Software License * ===================== * * NOTICE TO USER: * * BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND * CONDITIONS WHICH APPLY TO ITS USE. * * 1. The Software is owned by the IAU SOFA Board ("SOFA"). * * 2. Permission is granted to anyone to use the SOFA software for any * purpose, including commercial applications, free of charge and * without payment of royalties, subject to the conditions and * restrictions listed below. * * 3. You (the user) may copy and distribute SOFA source code to others, * and use and adapt its code and algorithms in your own software, * on a world-wide, royalty-free basis. That portion of your * distribution that does not consist of intact and unchanged copies * of SOFA source code files is a "derived work" that must comply * with the following requirements: * * a) Your work shall be marked or carry a statement that it * (i) uses routines and computations derived by you from * software provided by SOFA under license to you; and * (ii) does not itself constitute software provided by and/or * endorsed by SOFA. * * b) The source code of your derived work must contain descriptions * of how the derived work is based upon, contains and/or differs * from the original SOFA software. * * c) UNLIKE OTHER SOFA SOFTWARE, WHICH IS STRICTLY "READ ONLY", * USERS ARE PERMITTED TO REPLACE THIS SUBROUTINE WITH ONE USING * THE SAME NAME BUT DIFFERENT CODE. This is to allow use of * locally supported mechanisms for keeping track of leap * seconds, perhaps file or network based. It avoids the need for * applications to be relinked periodically in order to pick up * SOFA updates. * * c) The names of all routines in your derived work shall not * include the prefix "iau" or "sofa" or trivial modifications * thereof such as changes of case. * * d) The origin of the SOFA components of your derived work must * not be misrepresented; you must not claim that you wrote the * original software, nor file a patent application for SOFA * software or algorithms embedded in the SOFA software. * * e) These requirements must be reproduced intact in any source * distribution and shall apply to anyone to whom you have * granted a further right to modify the source code of your * derived work. * * Note that, as originally distributed, the SOFA software is * intended to be a definitive implementation of the IAU standards, * and consequently third-party modifications are discouraged. All * variations, no matter how minor, must be explicitly marked as * such, as explained above. * * 4. You shall not cause the SOFA software to be brought into * disrepute, either by misuse, or use for inappropriate tasks, or * by inappropriate modification. * * 5. The SOFA software is provided "as is" and SOFA makes no warranty * as to its use or performance. SOFA does not and cannot warrant * the performance or results which the user may obtain by using the * SOFA software. SOFA makes no warranties, express or implied, as * to non-infringement of third party rights, merchantability, or * fitness for any particular purpose. In no event will SOFA be * liable to the user for any consequential, incidental, or special * damages, including any lost profits or lost savings, even if a * SOFA representative has been advised of such damages, or for any * claim by any third party. * * 6. The provision of any version of the SOFA software under the terms * and conditions specified herein does not imply that future * versions will also be made available under the same terms and * conditions. * * In any published work or commercial product which uses the SOFA * software directly, acknowledgement (see www.iausofa.org) is * appreciated. * * Correspondence concerning SOFA software should be addressed as * follows: * * By email: sofa@ukho.gov.uk * By post: IAU SOFA Center * HM Nautical Almanac Office * UK Hydrographic Office * Admiralty Way, Taunton * Somerset, TA1 2DN * United Kingdom * *----------------------------------------------------------------------- END